Titanium material less susceptible to discoloration and method for production thereof

Abstract

Titanium material less susceptible to discoloration and method for thereof are provided. Titanium materials less susceptible to discoloration in the atmosphere are obtainable by controlling the fluorine and carbon contents in the oxide film on the surface thereof and the thickness of the oxide film. Such titanium materials are obtainable by dissolving the surface thereof in an aqueous fluonitric acid solution with a nitric acid concentration of not higher than 80 g/l or heat-treating at between 300 and 900° C. in a vacuum or in an inert gas atmosphere of argon or helium after dissolving in the aqueous fluonitric acid solution.

1. A method of manufacturing titanium material less susceptible to discoloration comprising annealing the titanium material prior to dissolving the surface of the titanium material in an aqueous solution of hydrofluoric and nitric acids; and thereafter, heating the titanium material at between 300 and 900° C. in a vacuum or an inert gas atmosphere after dissolving the surface of the titanium material in the aqueous solution of hydrofluoric and nitric acids;
 thereby providing the titanium material having an oxide film not more than 100 angstrom in thickness on the surface thereof containing not more than 3 at % fluorine and not more than 20 at % carbon in said oxide film. 
 
     
     
       2. A method of manufacturing titanium material less susceptible to discoloration according to  claim 1  comprising applying skin pass rolling, shot blasting or other surface properties adjusting or redressing either before or after, or both, dissolving in an aqueous fluonitric acid solution or either before or after, or both, heat treating in the vacuum or the inert gas atmosphere of argon or helium.